Related

Rails::Generator is a code generation
platform tailored for the Rails web application
framework. Generators are easily invoked within Rails applications to add and remove components
such as models and controllers. New generators are easy to create and may
be distributed as RubyGems, tarballs, or Rails
plugins for inclusion system-wide, per-user, or per-application.

For actual examples see the rails_generator/generators directory in the Rails source (or the railties directory if
you have frozen the Rails source in your
application).

Generators may subclass other generators to provide variations that require
little or no new logic but replace the template files.

For a RubyGem, put your generator class and templates in the lib
directory. For a Rails plugin, make a
generators directory at the root of your plugin.

The layout of generator files can be seen in the built-in
controller generator:

The directory name (controller) matches the name of the generator
file (controller_generator.rb) and class (ControllerGenerator). The files that
will be copied or used as templates are stored in the templates
directory.

The filenames of the templates don’t matter, but choose something
that will be self-explanatory since you will be referencing these in the
manifest method inside your generator subclass.